To get a sense of how far the Chinese leadership has come on the issue of climate change in a relatively short period, consider a conference held two years ago on the tropical island of Hainan, where, every year, China invites the high and mighty from around the world to address the weighty issues of the day at a plush resort. The theme of the conference was "Green China," and if there was a single underlying idea, it was that China, having just become the world's largest emitter of CO2 gases, was going to jump wholeheartedly on the global bandwagon to combat climate change. But on the conference's final day, during the main event and keynote address, President Hu Jintao talked about China's commitment to economic reform, to maintaining its extraordinary pace of economic growth, to opening China's market further to foreign investment and products  but only the barest nod in the direction of climate change. A confused American environmental consultant left the speech sputtering. "What was that about?" he asked former U.S. Secretary of State Colin Powell, who was walking out with him. Powell laughed. "You know what the first thing is that Hu Jintao doesn't think about when he wakes up every morning?" Powell joked. "Climate change."

Now, however, climate change for China has become the elephant in the room  an issue the country has to manage diplomatically as well as deal with substantively (two things that are emphatically not, from the government's standpoint, the same). Western environmental scientists and activists  who had directed most of their attention (and ire) at George W. Bush's U.S.  finally began embracing reality: China, with 1.3 billion people grasping the higher living standards that industrialization and market economics have brought, had only just begun to spew CO2 into the atmosphere, and it was already the No. 1 emitter. If climate change was the great global threat that the doomsayers believed it was and if there was to be a more effective global response post Kyoto (the 1997 treaty that failed, 96-0, in the U.S. Senate), China's emissions were going to have to be dealt with. And Beijing knew it. (See pictures of the world's most polluted places.)

Diplomatically, China began laying down public markers in advance of this December's U.N. summit on climate change in Copenhagen, which activists hope will succeed where Kyoto failed: getting governments to agree on enforceable reductions in carbon emissions. Earlier this summer, Beijing said it would commit to outright reductions of its CO2 emissions more than 40 years from now  by the year 2050. That two-generation time frame, which disappointed some critics, reflects a central reality in China. A lot of its leaders (not to mention its citizens) are deeply distrustful of the extreme rhetoric coming from the West on climate change. They see the developed world as having gotten rich one way and trying to change the rules just as China is on the brink of joining the club. The Chinese, concedes a Western diplomat in Beijing, want nothing to do with "ladder-up economics." (See pictures of the new Shanghai.)

And so on Tuesday at the U.N. General Assembly in New York City, Hu made a widely anticipated speech on climate change, finely calibrated for diplomatic effect. He was nothing if not cautious, saying  accurately  that China was in the process of increasing its energy efficiency, reducing the amount of energy required to produce a unit of GDP. Indeed, China's energy efficiency has improved in each of the past two years, a trend likely to continue, because a huge surge in investment in energy-intensive industries like steel and cement in the early part of this decade has run its course. New housing developments all over the country are also far more energy efficient. With that new energy efficiency, Hu said, will come a reduction in China's carbon intensity, the amount of CO2 it emits for every unit of GDP. This, too, is plausible, since enhanced energy efficiency tends to reduce carbon emissions at the same time. But the world was looking for targets  hard numbers  and all Hu would say was that China would cut, by a "notable margin," its emissions per unit of output by the year 2020. Out of such caution  standard in a country that does not want to do anything to hamstring its economic growth  it's unlikely that historic agreements will spring. (Has China become the climate-change good guy?)

While some observers were buoyed by Hu's statements, many environmental groups were disappointed. Most critics, however, have to temper their criticism. The irony is that China actually is developing renewable-energy sources faster than any other country in the world. Hu vowed yesterday that by 2020 renewable sources will account for 15% of China's total energy output  and there are industry analysts, both foreign and domestic, who believe that figure is probably conservative. The problem is that China is at the same time still investing massively in coal-fired electricity plants, the primary source of CO2 emissions, to meet its surging power demands. Overall, in 2009 China will probably add about 80 to 100 gigawatts of capacity to its electricity grid, and 75% to 80% of that will be from coal. In effect, says Gerald Page, managing director of Equinox Energy Partners in Beijing, a venture capital firm, China is adding 1 gigawatt of coal-fired capacity every five days. And that's not going to change anytime soon. (See pictures of the making of modern China.)

The message from Beijing is now unmistakable: Hu and his cohorts are no longer ignoring climate change. In fact, they're grappling with it in a way that was unthinkable just two years ago. But the Chinese have also made it clear they will deal with climate change at their own pace, with as little economic dislocation as possible. When Beijing says its carbon emissions won't begin to go down until 2050, that's not a bargaining position. That's reality, and the rest of the world has to deal with it.